An aneurysm is a degenerative dilation of a portion of a blood vessel that can ultimately lead to rupture of the vessel and life-threatening blood loss. As shown in FIG. 1, one of the most common sites of an aneurysm 105 is the infra-renal aorta 101 between the renal arteries 102 and the iliac vessels 106.
Referring now to FIG. 2, endovascular aneurysm repair (EVAR) is a minimally invasive procedure, which involves placing a tubular prosthesis 110 within the diseased blood vessel to act as an impervious liner which prevents the systemic pressure from pushing on the aneurysm 105. In particular, such prostheses 110 are generally made of a blood-impervious fabric such as polytetrafluorethylene (PTFE) or polyester (PET) that is supported along at least a portion of its length by a framework or skeleton. The framework or skeleton is commonly a metal (e.g., nitinol, stainless steel, chromium cobalt, etc.) or an injectable polymer. To be effective, the prosthesis must achieve circumferential wall apposition (or seal) with the inner wall of a healthy portion of the blood vessel, or vessels, proximal and distal to the aneurysm 105. For standard EVAR, the proximal seal is made in a healthy portion 104 of the aorta 101 distal to the openings 103 of the renal arteries 102. As shown in FIG. 2, since most infra-renal aneurysms extend to the terminal bifurcation of the aorta 101, most endovascular prostheses 110 for this location incorporate a bifurcated design, allowing for the distal seal to be achieved in each of the iliac vessels 106.
Referring still to FIG. 2, many endovascular prostheses 110 consist of a flat-topped fabric supported by a framework configured as a series of peaks and indentations. To achieve an effective seal, the proximal end of the graft 110 must have circumferential wall contact with the healthy portion 104 of the aorta 101. It is generally recommended that the longitudinal length of the healthy portion 104 of the aorta 101 be at least 15 mm to achieve a seal of sufficient length to ensure a long-term successful seal. However, in some cases, the aneurysm 105 arises too close to the renal arteries 102 to achieve this length of seal.
One known solution is to use an endoluminal graft with a scallop formed in the fabric of the endoluminal graft. A scallop, as used herein, is a deflection or discontinuity of the normally straight edge of the fabric of the endoluminal graft. Such scallops, can allow preservation of flow to important branch vessels such as the renal arteries that arise in the intended seal zone of the endoluminal graft. However, scallops require custom manufacture of a graft based on the patient's anatomy, an issue which is complicated when more than one scallop is required. Furthermore, extreme care must be taken to ensure that the scallops are properly aligned with the branch vessel during deployment of the endoluminal graft in order to avoid obstructing blood flow into the branch vessel.